Direction of DNA
DNA consists of two strands.
They are not identical, however they compliment each other.
Both strands run antiparallel to each other, meaning one strand is
inverted and opposite to the other.
They are not identical, however they compliment each other.
Both strands run antiparallel to each other, meaning one strand is
inverted and opposite to the other.
We look at DNA running from 5' to 3' or 3' to 5' when referring to the direction of DNA.
For further explanation, the sugars of the DNA can be
looked at. When zooming into the DNA, the structure consists of nitrogenous bases, phosphates, and sugars. The sugar of the DNA is a part of the "backbone" of the DNA, and it contains 5 carbons. These carbons are numbered right after the oxygens, and are counted in a clockwise manner (refer to picture). Carbon 1 is referred to as 1', carbon 2 is referred to as 2' and so on. This same counting process occurs on the other side of the backbone, however it is inverted, antiparallel. The strand on the left runs from 5' to 3', the strand on right runs from 3' to 5' DNA Polymerase only works from 5' to 3', so, the strand on the left is referred to as the leading strand. |
The other strand is referred to as the lagging strand, since DNA Polyermase
can only work from 5' to 3'.
can only work from 5' to 3'.
Because DNA Polymerase can only work from 5' to 3', RNA Primase lays down extra primers to guide the DNA Polymerase.
This requires more time and takes longer, thus calling this strand the lagging strand.
This requires more time and takes longer, thus calling this strand the lagging strand.